Well the idea is that when the South Koreans and US invade North Korea they will blow up the pillars at each end making the concrete barrier drop and block the road, preventing vehicles from moving north. The South Koreans have the same things. Here's a recent story about the SK ones: http://www.stripes.com/news/s-korea-s-overpasses-to-nowhere-remain-part-of-defense-strategy-1.106886